Connecting element

ABSTRACT

The invention relates to a fixing device consisting of a component ( 2 ) and a screw element ( 1 ) which comprises a force application ( 10 ) for a rotating tool. The component ( 2 ) and the screw element ( 1 ) co-operate with each other in a fixed state. A contact surface ( 11 ) of the screw element ( 1 ) is embodied as a convex outer surface ( 12 ) on the side thereof facing the component, and a contact surface ( 11 ) of the component ( 2 ) is embodied as a concave inner surface ( 16 ). The outer surface ( 12 ) and the inner surface ( 16 ) are arranged coaxially in relation to a common longitudinal axis (X-X) extending through the component ( 2 ) and the screw element ( 1 ). The contact surfaces ( 11 ) are defined in the axial section of the fixing device by curved sections which arc bent in such a way that the centre(s) of curvature (A; A 1 , A 2 ) of the convex outer surface ( 12 ) is/are set a perpendicularly to the longitudinal axis (X-X), from the centre(s) of curvature (B; B 1 , B 2 ) of the concave inner surface ( 16 ), the contact surfaces ( 11 ) being thereby fixed together by the ends of their curved sections.

[0001] The present invention concerns a fastener arrangement consisting of a component and a screw element with an area for the application of force for a turning tool, where the component and the screw element, when fastened to each other, are in contact with each other by way of contact surfaces, and where the contact surface of the screw element on the side facing the component, has a convexly curved outer surface, and where the contact surface of the component has a concavely curved inner surface, while the outer surface and the inner surface are positioned coaxially with respect to a common longitudinal axis, which runs through the component and the screw element.

[0002] The invention concerns also a screw element with an area for the application of force for a turning tool and a contact surface shaped as a convexly curved outer surface for contact with a concavely curved inner surface of a component, which contact surface points in the direction in which the screw element is screwed in, where the outer surface of the screw element and the inner surface of the component are positioned coaxially with respect to a longitudinal axis running through the component and the screw element.

[0003] Such fastener arrangements or screw elements are used, for example, for the attachment of automobile wheels or rims to a motor vehicle by means of wheel bolts.

[0004] In the case of known fasteners, it is a disadvantage that the outer surface of the screw element and/or the inner surface of the component are frequently deformed and damaged when the screw element is repeatedly screwed in, because the contact of the outer surface of the screw element, depending on the dimensioning of the screw element and the component, occurs either in the region of the front or rear edge, when viewed in the direction in which the screw element is screwed in, of the concavely curved inner surface of the component. Such deformations cause significant problems during assembly when a defined torque is selected. In addition, with the prevailing final tolerance stack-ups extremely variable load configurations result, namely so-called outer load supports and inner load supports, and thus strongly varying frictional moments result when the head makes contact.

[0005] The present invention is based on the objective of creating a fastener arrangement or a screw element of the same kind where the contact surfaces are deformed or damaged as little as possible even if they are loosened or fastened a number of times, and where, in addition, the extreme outer and inner load supports are to be avoided.

[0006] According to the invention this is achieved by the creation of a fastener arrangement, where the contact surfaces in an axial section of the fastener device are defined by arcuate sections curved in such a way, that the center(s) of curvature of the convexly curved outer surface extending in a direction perpendicular to the longitudinal axis is (are) located at such a distance from the center(s) of curvature of the concavely curved inner surface, that the contact surfaces, when they are fastened to each other, are located between the ends of their arc sections.

[0007] Furthermore, the objective is achieved by a screw element according to the invention, where the contact surfaces are defined, in an axial section of the screw element, by curved arc sections, the centers of curvature of which are located at such a distance from the longitudinal axis that the convexly curved outer surface and the concavely curved inner surface of the component, when they are fastened to each other, are in contact with each other between the ends of their arcuate sections.

[0008] The solutions in accordance with the invention are based on the recognition that the unfavorable forced contact conditions in the region of the front or rear edge, in the direction in which the screw is screwed in, of the concavely curved inner surface of the component, result from the fact that the centers of curvature of the curvature of the outer surface and the curvature of the inner surface are not spaced apart from each other in a direction vertical to the longitudinal axis. As a result, the contact between the outer surface and the inner surface occurs, when viewed in the direction in which the screw is screwed in, either at a front or a rear edge region of the inner surface.

[0009] Because of these unfavorable force conditions, deformations and damages of the outer and inner surfaces can occur, which result in an adverse effect on the fastening ability, for example, in the case of a defined torque.

[0010] In the case of a fastener arrangement in accordance with the invention, by means of creating a separation between the centers of curvature in a direction perpendicular to the longitudinal axis, a contact in the central region of the outer and inner surfaces in the direction of screw engagement is produced; however, the edge regions, which are relatively vulnerable to deformation, experience no load or a relatively low load. The fastener arrangement or the screw element, therefore, permit a fastening operation, even for multiple use, with a defined torque. In accordance with the invention, the overall load is reduced to such an extent that the diameter, which determines the friction moment, experiences only minor dimensional changes, so that ultimately only small changes in the desired tensioning forces occur.

[0011] Further advantageous design characteristics of the invention are contained in the subordinate claims as well as in the description below.

[0012] On the basis of an example of a preferred embodiment shown in the drawing, the invention will be explained in more detail below. The following is shown:

[0013]FIG. 1 an embodiment of the fastener arrangement in accordance with the invention in an axial section,

[0014]FIG. 2 a second embodiment of the fastener arrangement in accordance with the invention in an axial section.

[0015] In the different figures of the drawings equal parts are always shown with the same reference designations.

[0016]FIGS. 1 and 2 show, in an axial section through the longitudinal axis X-X, a screw element 1 in accordance with the invention, for example a screw, which can be screwed into a component 2 in the direction of thread engagement E. The screw element 1 shows a screw head 4 and threaded shaft 6 adjacent to it, with a screw point 8 located at its free end. The screw head 4 consists of a force application area 10 and a contact surface 11, which is turned toward the component 2, which contact surface is formed as a convexly curved outer surface 12, which curves around at least one center of curvature A. The area of force application 10 can, for example, be in the form of a hexagon, an interior hexagon, a slot, a cross recessed head, or the like. The component 2 has an opening 14 for the threaded shaft 6 and a contact surface 1I for receiving the convexly curved outer surface 12. The contact surface 11 is configured as an inner surface 16, which is concavely curved around at least one center of curvature B. The convexly curved outer surface 12 and the concavely curved inner surface 16 are coaxial with respect to a longitudinal axis X-X.

[0017] In the embodiment shown in FIG. 1 as an axial section, the outer surface 12 of the screw is convexly curved in such a manner that its centers of curvature A1, A2 are, in contrast to the center of curvature B of the inner surface 16, not located on the longitudinal axis X-X. This results in the fact that the contact does not occur at the front or rear edge region, when viewed in the direction in which the screw is screwed in, or at the ends of the concave or convex arc sections, but rather in the central region of the inner surface 16.

[0018] In FIG. 2 a second embodiment in accordance with the invention is shown in an axial section, where the inner surface 16 of component 2 is concavely curved in such a manner, that its centers of curvature B1, B2 are, in contrast to the center of curvature A of the outer surface 12, not located on the longitudinal axis X-X. This arrangement as well guarantees that the contact occurs not at the edge regions of the inner surface 16 or at the ends of the concave or convex arc sections.

[0019] The invention is not limited to the examples of the embodiment shown and described, but also includes all embodiments acting in an equivalent manner within the spirit of the invention; for example, a nut, which is threaded onto threaded shaft 6, can also serve as a screw element, which is located in a concavely curved inner surface 16. Also, a combination of the embodiments shown in FIGS. 1 and 2 is conceivable, where the arc section of the concavely curved inner surface 16 as well as the arc sections of the outer surface 12 are each curved in the axial section around two centers A1, A2; B1, B2. Furthermore, the arc sections cannot only be defined as circular sections, but also, for example, as elliptical sections.

[0020] Further, the invention is thus far also not limited to the combination of characteristics defined in claim 1, but it can also be defined by any possible combination of certain characteristics of all disclosed individual characteristics. This means that, in principle, any individual characteristic can practically be eliminated from claim 1, or can be replaced by at least one individual characteristic disclosed elsewhere in the application. To this extent, claim 1 must be understood as merely a first attempt of formulating an invention. 

1. Fastener arrangement, consisting of a component (2) and a screw element (1) with a force application area (10) for a turning tool, where the component (2) and the screw element (1)—when they have been attached—are in contact with each other by way of contact surfaces (11), and where the contact surface (11) of the screw element (1) on the side facing the component (2) is configured as a convexly curved outer surface (12), and the contact surface (11) of the component (2) is configured as a concavely curved inner surface (16), while the outer surface (12) and the inner surface (16) are positioned coaxially with respect to a common longitudinal axis (X-X), which extends through the component (2) and the screw element (1), characterized in that the contact surfaces (11) in the axial section of the fastener arrangement are defined as arc sections curved in such a manner, that the center(s) of curvature (A; A1, A2) of the convexly curved outer surface (12) is (are) spaced from the center(s) of curvature (B; B1, B2) of the concavely curved inner surface (16) in a direction proceeding perpendicularly to the longitudinal axis (X-X) in such a manner that the contact surfaces (11) are in contact with each other between the ends of their arc sections when they are fastened.
 2. Fastener arrangement according to claim 1, characterized in that the screw element (1) is configured as a screw consisting of a screw head (4) and a threaded shaft (6) which is adjacent to it, and with a free screw tip (8), where the convexly curved outer surface (12) is located on the side of the screw head (4) facing toward the threaded shaft (6).
 3. Fastener arrangement according to claim 1, characterized in that the screw element (1) is configured as a nut and the concavely curved inner surface (16) is located on the component (2) with a threaded shaft (6) extended in the direction of the nut.
 4. Fastener arrangement according to one of the claims 1 to 3, characterized in that arc sections which define the contact surfaces (11) are configured as circular sections.
 5. Fastener arrangement according to claim 4, characterized in that the circular sections of the concavely curved inner surface (16) have a common center of curvature B, and the circular sections of the convexly curved outer surface (12) have, in the direction extending perpendicularly to the longitudinal axis (X-X), centers of curvature A1, A2 spaced from each other, where the radius belonging to the circular sections of the concavely curved inner surface (16) is longer than the radii belonging to the circular sections of the convexly curved outer surface (12).
 6. Fastener arrangement according to claim 4, characterized in that the circular sections of the convexly curved outer surface (12) have a common center of curvature A, and the circular sections of the concavely curved inner surface (16) have, in the direction extending perpendicularly to the longitudinal axis (X-X), centers of curvature (B1, B2) spaced from each other, where the radius belonging to the circular sections of the convexly curved outer surface (12) is shorter than the radii belonging to the circular sections of the concavely curved inner surface (16).
 7. Fastener arrangement according to claim 4, characterized in that the circular sections of the concavely curved inner surface (16) and the circular sections of the convexly curved outer surface (12) always have—in the direction extending perpendicularly to the longitudinal axis (X-X)— centers of curvature (A1, A2, B1, B2) spaced from each other, where the centers of curvature (A1, A2, B1, B2) are spaced from each other in the direction perpendicular to the longitudinal axis (X-X), and where the radii belonging to the circular sections of the inner surface (16) are longer than the radii belonging to the circular sections of the outer surface (12).
 8. Fastener arrangement according to one of the claims 1 to 3, characterized in that the arc sections which define the contact surfaces (11) are configured as elliptical sections.
 9. Screw element (1) with a force application area (10) for a turning tool, and a contact surface (11) which points in the direction (E) in which the screw element (1) is screwed in, and which contact surface is configured as a convexly curved outer surface (12) for making contact with a concavely curved inner surface (16) of a component (2), where the outer surface (12) of the screw element (1) and the inner surface (16) of the component (2) are coaxial with respect to a common longitudinal axis (X-X) which extends through the component (2) and the screw element (1), characterized in that the contact surface (11) is defined in the axial section of the screw element (1) by curved arc sections, the centers of curvatures (A1, A2) of which are at such a spacing from the longitudinal axis (X-X) that the convexly curved outer surface (12) and the concavely curved inner surface (16) of the component (2) are in contact with each other between the ends of their arc sections when they are fastened to each other.
 10. Screw element according to claim 9, characterized by its construction as a screw, consisting of a screw head (4) and a threaded shaft (6) adjacent to it with a free screw point (8), where the convexly curved outer surface (12) is located on the side of the screw head (4), which side is facing the threaded shaft (6).
 11. Screw element according to claim 9, characterized by its configuration as a threaded nut.
 12. Screw element according to one of the claims (9 to 11), characterized in that the arc sections which define the contact surfaces (11) of the convexly curved outer surface (12) and the concavely curved inner surface (16) of the component (2) are configured as circular sections.
 13. Screw element according to claim 12, characterized in that the circular sections of the concavely curved inner surface (16) have a common center of curvature (B), and the circular sections of the convexly curved outer surface (12) in the direction extending perpendicularly to the longitudinal axis (X-X) have centers of curvature (A1, A2), which are spaced apart from each other, and where the radius belonging to the circular sections of the concavely curved inner surface (16) is longer than the radii of the circular sections of the convexly curved outer surface (12).
 14. Screw element according to claim 12, characterized in that the circular sections of the convexly curved outer surface (12) have a common center of curvature (A) and the circular sections of the concavely curved inner surface (16) in the direction extending perpendicularly to the longitudinal axis (X-X) have centers of curvature (B1, B2) spaced apart from each other, where the radius belonging to the circular sections of the convexly curved outer surface (12) is shorter than the radii of the circular sections of the concavely curved inner surface (16).
 15. Screw element according to claim 12, characterized in that the circular sections of the concavely curved inner surface (16) and the circular sections of the convexly curved outer surface (12) each have in the direction extending perpendicularly to the longitudinal axis (X-X) centers of curvature (A1, A2, B1, B2), which are spaced apart from each other, and where the centers of curvature (A1, A2, B1, B2), in the direction extending perpendicularly to the longitudinal axis (X-X) are spaced apart from each other, and where the radii belonging to the inner surface (16) of the circular sections are longer than the radii belonging to the circular sections of the outer surface (12).
 16. Screw element according to one of the claims 9 to 11, characterized in that the arc sections of the convexly curved outer surface (12), defining the contact surfaces (11), and the concavely curved inner surface (16) of the component (2) are configured as elliptical sections. 